Al(Ⅲ) speciation distribution and transformation in high concentration PACl solutions

Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the B （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.     

Effect of in-situ formed Al hydrates through long-term aging on enhanced particle destabilization by PACl coagulation

Aging of polyaluminum chloride (PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance. The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance. Two kinds of commercial coagulants (PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters. The results showed that CaSO₄ precipitation easily occur in a commercial PACl coagulant with time as it contains SO₄^2? and Ca²⁺. It also activates the precipitation of gibbsite Al(OH)₃ in PACl with aging. Through 180 days aging, both monomeric Al (Al_a) and polymeric Al (Al_b) substantially transform into colloidal Al (Al_c) and precipitated for both PACl coagulants. At low turbidity (10 NTU), PACl-1 has a superior turbidity reduction rate than PACl-2, while PACl-2 performs a little better turbidity reduction at high turbidity (1000 NTU) regardless of aging time. With aging time, an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU, while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Al_b mostly transform into Al_c after 150 days aging. It is concluded that dominant in-situ formed Al_c after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation, especially for low turbidity water, but the increase in preformed Al_c in PACl would worsen particle destabilization after aging.     

Al(Ⅲ) speciation distribution and transformation in high concentration PACl solutions

Effects of Al(Ⅲ) concentration and pH on the speciation of Al(Ⅲ) in polyaluminum chloride (PACl) solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al(Ⅲ) concentration from 0.01 to 2.0 mol/L with the B (OH/Al ratio) value from 1.0 to 2.5 by forced hydrolysis of AlCl3. The samples were characterized by ferron assay,pH and 27Al NMR. It was shown that the Al(Ⅲ) concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb (or Al13) decreased and Alc increased with increase of total Al(Ⅲ) concentration. Under the condition of Al(Ⅲ) 2.0 mol/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evolved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.     

Coagulation of micro-polluted Pearl River water with IPF-PACls

IntroductionThewaterqualityofnaturalriverisverycomplex,includingvariouskindsoforganic ,inorganicandbiologicalmatters,suchasthesolublemolecules,polymericmatters,colloids ,andsuspendedparticlessuchaslivebacteria ,algaeandalsoprotozoan (Tang,2 0 0 0 ) .Generally ,aquaticparticulatesaredispersivelysuspended ,ordepositintodiversesedimentsthroughadsorption ,aggregationandsedimentation.Furthermore ,theycanberesuspended ,transferredandconvertedundervariouswaterfluidconditions.Clearlydocumentedhistori…     

Interaction of PACls with sulfate

IntroductionPolyaluminumchloride (PACl)asamainkindofinorganicpolymerflocculantsisanewhighereffectivewaterandwastewatertreatmentreagent.Basedonthetraditionallow molecularaluminum ,ithasbeendevelopedworldwidesincethe 196 0s(Tang,1994 ;1990 ;1987) .PAClistheintermediateproductofthehydrolysis polymerization ageingprocessofAl(III)undersuitableconditions.Atpresent,itisgenerallyknownthattherearemanypossiblespeciesexistintheAl(III)solution ,suchasmonomers,oligomers,Al13 [AlO4Al12 (OH) 2 4(H2 …     

聚合氯化铝(PACl)混凝絮体的破碎与恢复

通过烧杯实验以及在线粒度监测考察了聚合氯化铝（PACl）混凝所生成絮体的破碎以及随后絮体的恢复情况.结果发现,絮体的破碎以及恢复情况因混凝区域的不同而呈现不同的规律.在稳定区,絮体的强度较大,不易破碎,且破碎后的絮体可进一步增长,其恢复因子高达259%;在电中和混凝区,絮体的强度最小,易于破碎,但破碎后可完全恢复;在再稳区和卷扫混凝区,絮体的强度较大,不易破碎,但破碎后不能完全恢复,其中后者的恢复因子仅为18.6％.再搅拌强度越大,对絮体的破碎及恢复程度的影响越大.对于卷扫混凝,经再搅拌破碎后而得到部分恢复的絮体,相对于未经再搅拌的絮体而言,其絮体层与水体间界面的沉降高度及平均沉降速率均较低,且在絮凝沉降区和区域沉降区,该絮体界面的瞬时沉降速率在同一絮体浓度下均较低,但在压缩沉降区,二者的瞬时沉降速率相同.     

Al(III) speciation distribution and transformation in high concentration PACl solutions

Introduction Since water pollution has become a worldwide problem, many countries suffered from lack of quantity of source water to high quality and safe water or both. Increased attention has been paid to the purification of water in recent years. The ef…     

聚合氯化铝和聚合硫酸铁对水中亚硒酸盐的去除研究

为达到快速有效去除饮用水中亚硒酸盐的目的,通过混凝法考察了聚合氯化铝与聚合硫酸铁对模拟硒污染饮用水源中亚硒酸盐的去除效果,探讨了初始浓度、投加量以及pH对去除效果的影响。结果表明,混凝工艺对水中亚硒酸盐的去除效果明显,在初始硒浓度为184／μg／L时,聚合氯化铝和聚合硫酸铁对亚硒酸盐的最大去除率分别为70％和97％。聚合硫酸铁对亚硒酸盐的混凝去除效果明显好于聚合氯化铝,其最佳除硒pH为8。     

Effects of pre-ozonation on organic matter removal by coagulation with IPF-PACI

Ozone plays an important role as a disinfectant and oxidant in potable water treatment practice and is increasingly being used as a pre-oxidant before coagulation. The purpose of this study is to obtain insight into the mechanisms that are operative in pre-ozonized coagulation. Effects ofpre-ozonation on organic matter removal during coagulation with IPF-PAC1 were investigated by using PDA （photometric disperse analysis）, apparent molecular weight distribution and chemical fractionation. The dynamic formation of flocs during coagulation process was detected. Changes of aquatic organic matter （AOM） structure resulted from the influence of pre-ozonation were evaluated. Results show that dosage of O3 and characteristics of AOM are two of the major factors influencing the performance of O3 on coagulation. No significant coagulation-aid effect of O3 was observed for all experiments using either A1C13 or PAC1. On the contrary, with the application of pre-ozonation, the coagulation efficiency of A1C13 was significantly deteriorated, reflected by the retardation of floc formation, and the removal decreases of turbidity, DOC, and UV254. However, if PACl was used instead of AlCl3, the adverse effects of pre-ozonation were mitigated obviously, particularly when the O3 dosage was less than 0.69 （mg O3/mg TOC）. The difference between removals of UV254, and DOC indicated that pre-ozonation greatly changed the molecular structure of AOM, but its capability of mineralization was not remarkable. Only 5% or so DOC was removed by pre-ozonation at 0.6--0.8 mg/L alone. Fractionation results showed that the organic products of pre-ozonation exhibited lower molecular weight and more hydrophilicity, which impaired the removal of DOC in the following coagulation process.     

工业聚合铝的形态分析方法研究

主要探讨了工业聚合铝 (PACl)的形态分析方法 ,即Al Ferron逐时络合比色法。重点研究了 2类Ferron比色液的稳定性及其对工业PACl形态分析的影响特征。